Your point is well taken. However, I must reiterate that wishing hindus “Holi Mubarak” is indirectly promoting their belief. It is clear that no muslim agrees with the religous basis and practices of hinduism. Thus, it is advisable that we stay as “tight-lipped” as possible concerning their festivals.
I know Islam teaches to respect other faiths which I violated and for this I am apologetic to the hindus. But to be honest, it is quite disappointing to see a fellow muslim brother going out of his way to please non-muslims. A better coarse of action would have been to totally igonore this topic.